async function test() { (async () => { var a = await this.test1(); var b = await this.test2(a); var c = await this.test3(b); this.doThis(a,b,c); })(); } What does it mean to put methods (test1,test2,test3) inside async () => {})()? I find it faster than
async function test() { var a = await this.test1(); var b = await this.test2(a); var c = await this.test3(b); this.doThis(a,b,c); } Any downside of using it?
Both return a promise but they return different promises.
The first will return a promise that may resolve before this.test1()'s result resolves.
The second returns a promise that only resolves after the final call to this.doThis(a,b,c);.
This has been called the "fire and forget pattern":
Often in application development you want a process to call another thread and continue the process flow, without waiting for a response from the called thread. This pattern is called the “fire and forget” pattern.
You can see this in
function logEventually(str) { return new Promise((resolve) => { setTimeout(() => { console.log(str); resolve(null); }, 0); }); } async function a() { await logEventually('in a 1'); await logEventually('in a 2'); await logEventually('in a 3'); return await logEventually('end of a'); } async function b() { (async () => { await logEventually('in b 1'); await logEventually('in b 2'); await logEventually('in b 3'); })(); return await logEventually('end of b'); } a(); b();
(async () => {})();this.doThis(a,b,c); even before it resolves this.test1();, doesn't it mean that this.doThis(a,b,c); would error out?
await statements.
return Promise.resolve();in the first case, which isn't useful at all.(async () => { })();?async/awaitsyntax. If that expression exists within another function, it means the caller of that function will not be able to know when the asynchronous calls have completed.